A fuel cell is of a system that generates electric power in a mode of extracting electromotive force based on an electrochemical reaction of fuel (example: gaseous hydrogen) and an oxidizer (example: air) to an outside of a reaction mechanism. The fuel cell does not generate a harmful emission, and contributes to the environmental conservation.
A cell in which a power generation mechanism of the fuel cell system is formed into a single configuration is referred to as a “single cell”. A multiple cell in which a plurality of the single cells are stacked on one another and are electrically interconnected is referred to as a “fuel cell stack” or simply as a “stack”.
In the case of a polymer electrolyte fuel cell, each of the single cells which compose the fuel cell stack has a substantially plate-like structure in which an electrode layer and a gas diffusion layer are arranged on positive and negative electrodes of a solid polymer electrolyte membrane, respectively. Each single cell is physically separated from the single cell adjacent thereto by a sheet-like positive electrode or negative electrode separator (hereinafter, often generically referred to as a “fuel cell separator” or simply as a “separator”) attached onto an outside of the electrode layer or the gas diffusion layer.
Such single-cell power generation mechanisms adjacent to each other are separated from each other by a set of the positive electrode and negative electrode separators adjacent to each other. Hence, the set of separators is also called the “separator”. Hereinafter, according to needs, the set of separators will be referred to as a “separator unit” or a “separator adhesion body”, and will be distinguished from the positive electrode or negative electrode separators.
The fuel, the oxidizer, and a cooling medium (example: a coolant) are included in utilities of the single-cell power generation mechanism. Each of the separators defines passages (that is, a fuel passage, an oxidizer passage, and a cooling medium passage) which supply the utilities to or circulate the utilities through the power generation mechanisms related to the separator concerned.
These passages are defined by surface regions (example: an uneven surface, a groove surface, a through-holed inner wall surface) of the separator, which are related to the passages concerned. Hence, these surface regions are subjected to processing treatments corresponding thereto.
Each separator of the fuel cell is molded by using a die that follows passage patterns corresponding to the separator concerned. For example, the separator is molded by a method of compressing a mixture of carbon and thermosetting resin. There is a cutting method of performing cutting processing (for example, groove cutting) for a blank material (a flat plate on which grooves are not cut) of the separator. The cutting method has advantages that dimensional accuracy in the cutting processing is good and that a deflection of the separator is small; however, the above-described molding method is mainly used in terms of production efficiency.
The fuel cell stack requires a sealing material that seals the utilities. A compression gasket or an adhesive is usually used as the sealing material.
In the case of using the adhesive as the sealing material, the adhesive is coated on individual separators, and the plurality of separators on which the adhesive is coated are stacked on one another, and then the adhesive is cured to adhere and join these separators to one another.
Development of an adhesion method and adhesion apparatus of the separators by using the adhesive has been being progressed.
Japanese Patent Laid-Open Publication No. 2004-6419 discloses a technology for coating the adhesive with a uniform thickness on the separators, and equalizing surface pressures applied to stacked surfaces of such stacked members that compose the fuel cell stack, thereby reducing an internal resistance of the fuel cell, and preventing a mixing or leakage of the fuel.
Japanese Patent Laid-Open Publication No. 2003-22827 discloses a technology for correcting the deflection of the separators by using a negative pressure.